mcs/mcs/namespace.cs

   1 //
   2 // namespace.cs: Tracks namespaces
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Marek Safar (marek.safar@seznam.cz)
   7 //
   8 // (C) 2001 Ximian, Inc.
   9 //
  10 using System;
  11 using System.Collections;
  12 using System.Collections.Specialized;
  13 using System.Reflection;
  14
  15 namespace Mono.CSharp {
  16
  17         public class RootNamespace : Namespace {
  18                 static MethodInfo get_namespaces_method;
  19
  20                 string alias_name;
  21                 Assembly referenced_assembly;
  22
  23                 Hashtable all_namespaces;
  24
  25                 static Hashtable root_namespaces;
  26                 public static GlobalRootNamespace Global;
  27
  28                 static RootNamespace ()
  29                 {
  30                         get_namespaces_method = typeof (Assembly).GetMethod ("GetNamespaces", BindingFlags.Instance | BindingFlags.NonPublic);
  31
  32                         Reset ();
  33                 }
  34
  35                 public static void Reset ()
  36                 {
  37                         root_namespaces = new Hashtable ();
  38                         Global = new GlobalRootNamespace ();
  39                         root_namespaces ["global"] = Global;
  40                 }
  41
  42                 protected RootNamespace (string alias_name, Assembly assembly)
  43                         : base (null, String.Empty)
  44                 {
  45                         this.alias_name = alias_name;
  46                         referenced_assembly = assembly;
  47
  48                         all_namespaces = new Hashtable ();
  49                         all_namespaces.Add ("", this);
  50
  51                         if (referenced_assembly != null)
  52                                 ComputeNamespaces (this.referenced_assembly);
  53                 }
  54
  55                 public static void DefineRootNamespace (string name, Assembly assembly)
  56                 {
  57                         if (name == "global") {
  58                                 NamespaceEntry.Error_GlobalNamespaceRedefined (Location.Null);
  59                                 return;
  60                         }
  61                         RootNamespace retval = GetRootNamespace (name);
  62                         if (retval == null || retval.referenced_assembly != assembly)
  63                                 root_namespaces [name] = new RootNamespace (name, assembly);
  64                 }
  65
  66                 public static RootNamespace GetRootNamespace (string name)
  67                 {
  68                         return (RootNamespace) root_namespaces [name];
  69                 }
  70
  71                 public virtual Type LookupTypeReflection (string name, Location loc)
  72                 {
  73                         return GetTypeInAssembly (referenced_assembly, name);
  74                 }
  75
  76                 public void RegisterNamespace (Namespace child)
  77                 {
  78                         if (child != this)
  79                                 all_namespaces.Add (child.Name, child);
  80                 }
  81
  82                 public bool IsNamespace (string name)
  83                 {
  84                         return all_namespaces.Contains (name);
  85                 }
  86
  87                 protected void RegisterNamespace (string dotted_name)
  88                 {
  89                         if (dotted_name != null && dotted_name.Length != 0 && ! IsNamespace (dotted_name))
  90                                 GetNamespace (dotted_name, true);
  91                 }
  92
  93                 protected void ComputeNamespaces (Assembly assembly)
  94                 {
  95                         if (get_namespaces_method != null) {
  96                                 string [] namespaces = (string []) get_namespaces_method.Invoke (assembly, null);
  97                                 foreach (string ns in namespaces)
  98                                         RegisterNamespace (ns);
  99                                 return;
 100                         }
 101
 102                         foreach (Type t in assembly.GetExportedTypes ())
 103                                 RegisterNamespace (t.Namespace);
 104                 }
 105
 106                 protected static Type GetTypeInAssembly (Assembly assembly, string name)
 107                 {
 108                         Type t = assembly.GetType (name);
 109                         if (t == null)
 110                                 return null;
 111
 112                         if (t.IsPointer)
 113                                 throw new InternalErrorException ("Use GetPointerType() to get a pointer");
 114
 115                         TypeAttributes ta = t.Attributes & TypeAttributes.VisibilityMask;
 116                         if (ta == TypeAttributes.NestedPrivate)
 117                                 return null;
 118
 119                         if ((ta == TypeAttributes.NotPublic ||
 120                              ta == TypeAttributes.NestedAssembly ||
 121                              ta == TypeAttributes.NestedFamANDAssem) &&
 122                             !TypeManager.IsFriendAssembly (t.Assembly))
 123                                 return null;
 124
 125                         return t;
 126                 }
 127
 128                 public override string ToString ()
 129                 {
 130                         return String.Format ("RootNamespace ({0}::)", alias_name);
 131                 }
 132
 133                 public override string GetSignatureForError ()
 134                 {
 135                         return alias_name + "::";
 136                 }
 137         }
 138
 139         public class GlobalRootNamespace : RootNamespace {
 140                 Assembly [] assemblies;
 141                 Module [] modules;
 142
 143                 public GlobalRootNamespace ()
 144                         : base ("global", null)
 145                 {
 146                         assemblies = new Assembly [0];
 147                 }
 148
 149                 public Assembly [] Assemblies {
 150                         get { return assemblies; }
 151                 }
 152
 153                 public Module [] Modules {
 154                         get { return modules; }
 155                 }
 156
 157                 public void AddAssemblyReference (Assembly a)
 158                 {
 159                         foreach (Assembly assembly in assemblies) {
 160                                 if (a == assembly)
 161                                         return;
 162                         }
 163
 164                         int top = assemblies.Length;
 165                         Assembly [] n = new Assembly [top + 1];
 166                         assemblies.CopyTo (n, 0);
 167                         n [top] = a;
 168                         assemblies = n;
 169
 170                         ComputeNamespaces (a);
 171                 }
 172
 173                 public void AddModuleReference (Module m)
 174                 {
 175                         int top = modules != null ? modules.Length : 0;
 176                         Module [] n = new Module [top + 1];
 177                         if (modules != null)
 178                                 modules.CopyTo (n, 0);
 179                         n [top] = m;
 180                         modules = n;
 181
 182                         if (m == CodeGen.Module.Builder)
 183                                 return;
 184
 185                         foreach (Type t in m.GetTypes ())
 186                                 RegisterNamespace (t.Namespace);
 187                 }
 188
 189                 public override void Error_NamespaceDoesNotExist(DeclSpace ds, Location loc, string name)
 190                 {
 191                         Report.Error (400, loc, "The type or namespace name `{0}' could not be found in the global namespace (are you missing an assembly reference?)",
 192                                 name);
 193                 }
 194
 195                 public override Type LookupTypeReflection (string name, Location loc)
 196                 {
 197                         Type found_type = null;
 198
 199                         foreach (Assembly a in assemblies) {
 200                                 Type t = GetTypeInAssembly (a, name);
 201                                 if (t == null)
 202                                         continue;
 203
 204                                 if (found_type == null) {
 205                                         found_type = t;
 206                                         continue;
 207                                 }
 208
 209                                 Report.SymbolRelatedToPreviousError (found_type);
 210                                 Report.SymbolRelatedToPreviousError (t);
 211                                 Report.Error (433, loc, "The imported type `{0}' is defined multiple times", name);
 212
 213                                 return found_type;
 214                         }
 215
 216                         if (modules != null) {
 217                                 foreach (Module module in modules) {
 218                                         Type t = module.GetType (name);
 219                                         if (t == null)
 220                                                 continue;
 221
 222                                         if (found_type == null) {
 223                                                 found_type = t;
 224                                                 continue;
 225                                         }
 226
 227                                         Report.SymbolRelatedToPreviousError (found_type);
 228                                         if (loc.IsNull) {
 229                                                 DeclSpace ds = TypeManager.LookupDeclSpace (t);
 230                                                 Report.Warning (1685, 1, ds.Location, "The type `{0}' conflicts with the predefined type `{1}' and will be ignored",
 231                                                         ds.GetSignatureForError (), TypeManager.CSharpName (found_type));
 232                                                 return found_type;
 233                                         }
 234                                         Report.SymbolRelatedToPreviousError (t);
 235                                         Report.Warning (436, 2, loc, "The type `{0}' conflicts with the imported type `{1}'. Ignoring the imported type definition",
 236                                                 TypeManager.CSharpName (t), TypeManager.CSharpName (found_type));
 237                                         return t;
 238                                 }
 239                         }
 240
 241                         return found_type;
 242                 }
 243         }
 244
 245         /// <summary>
 246         ///   Keeps track of the namespaces defined in the C# code.
 247         ///
 248         ///   This is an Expression to allow it to be referenced in the
 249         ///   compiler parse/intermediate tree during name resolution.
 250         /// </summary>
 251         public class Namespace : FullNamedExpression {
 252
 253                 Namespace parent;
 254                 string fullname;
 255                 IDictionary namespaces;
 256                 IDictionary declspaces;
 257                 Hashtable cached_types;
 258                 RootNamespace root;
 259
 260                 public readonly MemberName MemberName;
 261
 262                 /// <summary>
 263                 ///   Constructor Takes the current namespace and the
 264                 ///   name.  This is bootstrapped with parent == null
 265                 ///   and name = ""
 266                 /// </summary>
 267                 public Namespace (Namespace parent, string name)
 268                 {
 269                         // Expression members.
 270                         this.eclass = ExprClass.Namespace;
 271                         this.Type = typeof (Namespace);
 272                         this.loc = Location.Null;
 273
 274                         this.parent = parent;
 275
 276                         if (parent != null)
 277                                 this.root = parent.root;
 278                         else
 279                                 this.root = this as RootNamespace;
 280
 281                         if (this.root == null)
 282                                 throw new InternalErrorException ("Root namespaces must be created using RootNamespace");
 283
 284                         string pname = parent != null ? parent.Name : "";
 285
 286                         if (pname == "")
 287                                 fullname = name;
 288                         else
 289                                 fullname = parent.Name + "." + name;
 290
 291                         if (fullname == null)
 292                                 throw new InternalErrorException ("Namespace has a null fullname");
 293
 294                         if (parent != null && parent.MemberName != MemberName.Null)
 295                                 MemberName = new MemberName (parent.MemberName, name);
 296                         else if (name.Length == 0)
 297                                 MemberName = MemberName.Null;
 298                         else
 299                                 MemberName = new MemberName (name);
 300
 301                         namespaces = new HybridDictionary ();
 302                         cached_types = new Hashtable ();
 303
 304                         root.RegisterNamespace (this);
 305                 }
 306
 307                 public override Expression DoResolve (EmitContext ec)
 308                 {
 309                         return this;
 310                 }
 311
 312                 public virtual void Error_NamespaceDoesNotExist (DeclSpace ds, Location loc, string name)
 313                 {
 314                         if (name.IndexOf ('`') > 0) {
 315                                 FullNamedExpression retval = Lookup (ds, SimpleName.RemoveGenericArity (name), loc);
 316                                 if (retval != null) {
 317                                         Error_TypeArgumentsCannotBeUsed (retval.Type, loc, "type");
 318                                         return;
 319                                 }
 320                         } else {
 321                                 Type t = LookForAnyGenericType (name);
 322                                 if (t != null) {
 323                                         Error_InvalidNumberOfTypeArguments (t, loc);
 324                                         return;
 325                                 }
 326                         }
 327
 328                         Report.Error (234, loc, "The type or namespace name `{0}' does not exist in the namespace `{1}'. Are you missing an assembly reference?",
 329                                 name, FullName);
 330                 }
 331
 332                 public static void Error_InvalidNumberOfTypeArguments (Type t, Location loc)
 333                 {
 334                         Report.SymbolRelatedToPreviousError (t);
 335                         Report.Error (305, loc, "Using the generic type `{0}' requires `{1}' type argument(s)",
 336                                 TypeManager.CSharpName(t), TypeManager.GetNumberOfTypeArguments(t).ToString());
 337                 }
 338
 339                 public static void Error_TypeArgumentsCannotBeUsed(Type t, Location loc, string symbol)
 340                 {
 341                         Report.SymbolRelatedToPreviousError(t);
 342                         Report.Error(308, loc, "The non-generic {0} `{1}' cannot be used with the type argument(s)",
 343                                 symbol, TypeManager.CSharpName(t));
 344                 }
 345
 346                 public override void Emit (EmitContext ec)
 347                 {
 348                         throw new InternalErrorException ("Expression tree referenced namespace " + fullname + " during Emit ()");
 349                 }
 350
 351                 public override string GetSignatureForError ()
 352                 {
 353                         return Name;
 354                 }
 355
 356                 public Namespace GetNamespace (string name, bool create)
 357                 {
 358                         int pos = name.IndexOf ('.');
 359
 360                         Namespace ns;
 361                         string first;
 362                         if (pos >= 0)
 363                                 first = name.Substring (0, pos);
 364                         else
 365                                 first = name;
 366
 367                         ns = (Namespace) namespaces [first];
 368                         if (ns == null) {
 369                                 if (!create)
 370                                         return null;
 371
 372                                 ns = new Namespace (this, first);
 373                                 namespaces.Add (first, ns);
 374                         }
 375
 376                         if (pos >= 0)
 377                                 ns = ns.GetNamespace (name.Substring (pos + 1), create);
 378
 379                         return ns;
 380                 }
 381
 382                 TypeExpr LookupType (string name, Location loc)
 383                 {
 384                         if (cached_types.Contains (name))
 385                                 return cached_types [name] as TypeExpr;
 386
 387                         Type t = null;
 388                         if (declspaces != null) {
 389                                 DeclSpace tdecl = declspaces [name] as DeclSpace;
 390                                 if (tdecl != null) {
 391                                         //
 392                                         // Note that this is not:
 393                                         //
 394                                         //   t = tdecl.DefineType ()
 395                                         //
 396                                         // This is to make it somewhat more useful when a DefineType
 397                                         // fails due to problems in nested types (more useful in the sense
 398                                         // of fewer misleading error messages)
 399                                         //
 400                                         tdecl.DefineType ();
 401                                         t = tdecl.TypeBuilder;
 402                                 }
 403                         }
 404                         string lookup = t != null ? t.FullName : (fullname.Length == 0 ? name : fullname + "." + name);
 405                         Type rt = root.LookupTypeReflection (lookup, loc);
 406
 407                         // HACK: loc.IsNull when the type is core type
 408                         if (t == null || (rt != null && loc.IsNull))
 409                                 t = rt;
 410
 411                         TypeExpr te = t == null ? null : new TypeExpression (t, Location.Null);
 412                         cached_types [name] = te;
 413                         return te;
 414                 }
 415
 416                 ///
 417                 /// Used for better error reporting only
 418                 ///
 419                 public Type LookForAnyGenericType (string typeName)
 420                 {
 421                         if (declspaces == null)
 422                                 return null;
 423
 424                         typeName = SimpleName.RemoveGenericArity (typeName);
 425
 426                         foreach (DictionaryEntry de in declspaces) {
 427                                 string type_item = (string) de.Key;
 428                                 int pos = type_item.LastIndexOf ('`');
 429                                 if (pos == typeName.Length && String.Compare (typeName, 0, type_item, 0, pos) == 0)
 430                                         return ((DeclSpace) de.Value).TypeBuilder;
 431                         }
 432                         return null;
 433                 }
 434
 435                 public FullNamedExpression Lookup (DeclSpace ds, string name, Location loc)
 436                 {
 437                         if (namespaces.Contains (name))
 438                                 return (Namespace) namespaces [name];
 439
 440                         TypeExpr te = LookupType (name, loc);
 441                         if (te == null || !ds.CheckAccessLevel (te.Type))
 442                                 return null;
 443
 444                         return te;
 445                 }
 446
 447                 public void AddDeclSpace (string name, DeclSpace ds)
 448                 {
 449                         if (declspaces == null)
 450                                 declspaces = new HybridDictionary ();
 451                         declspaces.Add (name, ds);
 452                 }
 453
 454                 /// <summary>
 455                 ///   The qualified name of the current namespace
 456                 /// </summary>
 457                 public string Name {
 458                         get { return fullname; }
 459                 }
 460
 461                 public override string FullName {
 462                         get { return fullname; }
 463                 }
 464
 465                 /// <summary>
 466                 ///   The parent of this namespace, used by the parser to "Pop"
 467                 ///   the current namespace declaration
 468                 /// </summary>
 469                 public Namespace Parent {
 470                         get { return parent; }
 471                 }
 472
 473                 public override string ToString ()
 474                 {
 475                         return String.Format ("Namespace ({0})", Name);
 476                 }
 477         }
 478
 479         public class NamespaceEntry {
 480                 Namespace ns;
 481                 NamespaceEntry parent, implicit_parent;
 482                 SourceFile file;
 483                 int symfile_id;
 484                 Hashtable aliases;
 485                 ArrayList using_clauses;
 486                 public bool DeclarationFound = false;
 487                 bool UsingFound;
 488
 489                 public readonly DeclSpace SlaveDeclSpace;
 490
 491                 ListDictionary extern_aliases;
 492
 493                 static ArrayList entries = new ArrayList ();
 494
 495                 public static void Reset ()
 496                 {
 497                         entries = new ArrayList ();
 498                 }
 499
 500                 //
 501                 // This class holds the location where a using definition is
 502                 // done, and whether it has been used by the program or not.
 503                 //
 504                 // We use this to flag using clauses for namespaces that do not
 505                 // exist.
 506                 //
 507                 public class UsingEntry : IResolveContext {
 508                         public readonly MemberName Name;
 509                         readonly NamespaceEntry NamespaceEntry;
 510                         readonly Location Location;
 511
 512                         public UsingEntry (NamespaceEntry entry, MemberName name, Location loc)
 513                         {
 514                                 Name = name;
 515                                 NamespaceEntry = entry;
 516                                 Location = loc;
 517                         }
 518
 519                         internal Namespace resolved;
 520
 521                         public Namespace Resolve ()
 522                         {
 523                                 if (resolved != null)
 524                                         return resolved;
 525
 526                                 FullNamedExpression fne = Name.GetTypeExpression ().ResolveAsTypeStep (this, false);
 527                                 if (fne == null) {
 528                                         Error_NamespaceNotFound (Location, Name.ToString ());
 529                                         return null;
 530                                 }
 531
 532                                 resolved = fne as Namespace;
 533                                 if (resolved == null) {
 534                                         Report.SymbolRelatedToPreviousError (fne.Type);
 535                                         Report.Error (138, Location,
 536                                                 "`{0}' is a type not a namespace. A using namespace directive can only be applied to namespaces", Name.ToString ());
 537                                 }
 538                                 return resolved;
 539                         }
 540
 541                         DeclSpace IResolveContext.DeclContainer {
 542                                 get { return NamespaceEntry.SlaveDeclSpace; }
 543                         }
 544
 545                         DeclSpace IResolveContext.GenericDeclContainer {
 546                                 get { return NamespaceEntry.SlaveDeclSpace; }
 547                         }
 548
 549                         bool IResolveContext.IsInObsoleteScope {
 550                                 get { return false; }
 551                         }
 552                         bool IResolveContext.IsInUnsafeScope {
 553                                 get { return false; }
 554                         }
 555                 }
 556
 557                 public abstract class AliasEntry {
 558                         public readonly string Name;
 559                         public readonly NamespaceEntry NamespaceEntry;
 560                         public readonly Location Location;
 561
 562                         protected AliasEntry (NamespaceEntry entry, string name, Location loc)
 563                         {
 564                                 Name = name;
 565                                 NamespaceEntry = entry;
 566                                 Location = loc;
 567                         }
 568
 569                         protected FullNamedExpression resolved;
 570                         bool error;
 571
 572                         public FullNamedExpression Resolve ()
 573                         {
 574                                 if (resolved != null || error)
 575                                         return resolved;
 576                                 resolved = DoResolve ();
 577                                 if (resolved == null)
 578                                         error = true;
 579                                 return resolved;
 580                         }
 581
 582                         protected abstract FullNamedExpression DoResolve ();
 583                 }
 584
 585                 public class LocalAliasEntry : AliasEntry, IResolveContext {
 586                         public readonly Expression Alias;
 587
 588                         public LocalAliasEntry (NamespaceEntry entry, string name, MemberName alias, Location loc) :
 589                                 base (entry, name, loc)
 590                         {
 591                                 Alias = alias.GetTypeExpression ();
 592                         }
 593
 594                         protected override FullNamedExpression DoResolve ()
 595                         {
 596                                 resolved = Alias.ResolveAsTypeStep (this, false);
 597                                 if (resolved == null)
 598                                         return null;
 599
 600                                 if (resolved.Type != null) {
 601                                         TypeAttributes attr = resolved.Type.Attributes & TypeAttributes.VisibilityMask;
 602                                         if (attr == TypeAttributes.NestedPrivate || attr == TypeAttributes.NestedFamily ||
 603                                                 ((attr == TypeAttributes.NestedFamORAssem || attr == TypeAttributes.NestedAssembly) &&
 604                                                 TypeManager.LookupDeclSpace (resolved.Type) == null)) {
 605                                                 Expression.ErrorIsInaccesible (Alias.Location, Alias.ToString ());
 606                                                 return null;
 607                                         }
 608                                 }
 609
 610                                 return resolved;
 611                         }
 612
 613                         DeclSpace IResolveContext.DeclContainer {
 614                                 get { return NamespaceEntry.SlaveDeclSpace; }
 615                         }
 616
 617                         DeclSpace IResolveContext.GenericDeclContainer {
 618                                 get { return NamespaceEntry.SlaveDeclSpace; }
 619                         }
 620
 621                         bool IResolveContext.IsInObsoleteScope {
 622                                 get { return false; }
 623                         }
 624                         bool IResolveContext.IsInUnsafeScope {
 625                                 get { return false; }
 626                         }
 627                 }
 628
 629                 public class ExternAliasEntry : AliasEntry {
 630                         public ExternAliasEntry (NamespaceEntry entry, string name, Location loc) :
 631                                 base (entry, name, loc)
 632                         {
 633                         }
 634
 635                         protected override FullNamedExpression DoResolve ()
 636                         {
 637                                 resolved = RootNamespace.GetRootNamespace (Name);
 638                                 if (resolved == null)
 639                                         Report.Error (430, Location, "The extern alias '" + Name +
 640                                                                         "' was not specified in a /reference option");
 641
 642                                 return resolved;
 643                         }
 644                 }
 645
 646                 public NamespaceEntry (NamespaceEntry parent, SourceFile file, string name)
 647                 {
 648                         this.parent = parent;
 649                         this.file = file;
 650                         entries.Add (this);
 651                         this.ID = entries.Count;
 652
 653                         if (parent != null)
 654                                 ns = parent.NS.GetNamespace (name, true);
 655                         else if (name != null)
 656                                 ns = RootNamespace.Global.GetNamespace (name, true);
 657                         else
 658                                 ns = RootNamespace.Global;
 659                         SlaveDeclSpace = new RootDeclSpace (this);
 660                 }
 661
 662                 private NamespaceEntry (NamespaceEntry parent, SourceFile file, Namespace ns, bool slave)
 663                 {
 664                         this.parent = parent;
 665                         this.file = file;
 666                         // no need to add self to 'entries', since we don't have any aliases or using entries.
 667                         this.ID = -1;
 668                         this.IsImplicit = true;
 669                         this.ns = ns;
 670                         this.SlaveDeclSpace = slave ? new RootDeclSpace (this) : null;
 671                 }
 672
 673                 //
 674                 // According to section 16.3.1 (using-alias-directive), the namespace-or-type-name is
 675                 // resolved as if the immediately containing namespace body has no using-directives.
 676                 //
 677                 // Section 16.3.2 says that the same rule is applied when resolving the namespace-name
 678                 // in the using-namespace-directive.
 679                 //
 680                 // To implement these rules, the expressions in the using directives are resolved using
 681                 // the "doppelganger" (ghostly bodiless duplicate).
 682                 //
 683                 NamespaceEntry doppelganger;
 684                 NamespaceEntry Doppelganger {
 685                         get {
 686                                 if (!IsImplicit && doppelganger == null)
 687                                         doppelganger = new NamespaceEntry (ImplicitParent, file, ns, true);
 688                                 return doppelganger;
 689                         }
 690                 }
 691
 692                 public readonly int ID;
 693                 public readonly bool IsImplicit;
 694
 695                 public Namespace NS {
 696                         get { return ns; }
 697                 }
 698
 699                 public NamespaceEntry Parent {
 700                         get { return parent; }
 701                 }
 702
 703                 public NamespaceEntry ImplicitParent {
 704                         get {
 705                                 if (parent == null)
 706                                         return null;
 707                                 if (implicit_parent == null) {
 708                                         implicit_parent = (parent.NS == ns.Parent)
 709                                                 ? parent
 710                                                 : new NamespaceEntry (parent, file, ns.Parent, false);
 711                                 }
 712                                 return implicit_parent;
 713                         }
 714                 }
 715
 716                 /// <summary>
 717                 ///   Records a new namespace for resolving name references
 718                 /// </summary>
 719                 public void Using (MemberName name, Location loc)
 720                 {
 721                         if (DeclarationFound){
 722                                 Report.Error (1529, loc, "A using clause must precede all other namespace elements except extern alias declarations");
 723                                 return;
 724                         }
 725
 726                         UsingFound = true;
 727
 728                         if (name.Equals (ns.MemberName))
 729                                 return;
 730
 731                         if (using_clauses == null)
 732                                 using_clauses = new ArrayList ();
 733
 734                         foreach (UsingEntry old_entry in using_clauses) {
 735                                 if (name.Equals (old_entry.Name)) {
 736                                         Report.Warning (105, 3, loc, "The using directive for `{0}' appeared previously in this namespace", name.GetName ());
 737                                         return;
 738                                 }
 739                         }
 740
 741                         UsingEntry ue = new UsingEntry (Doppelganger, name, loc);
 742                         using_clauses.Add (ue);
 743                 }
 744
 745                 public void UsingAlias (string name, MemberName alias, Location loc)
 746                 {
 747                         if (DeclarationFound){
 748                                 Report.Error (1529, loc, "A using clause must precede all other namespace elements except extern alias declarations");
 749                                 return;
 750                         }
 751
 752                         UsingFound = true;
 753
 754                         if (aliases == null)
 755                                 aliases = new Hashtable ();
 756
 757                         if (aliases.Contains (name)) {
 758                                 AliasEntry ae = (AliasEntry) aliases [name];
 759                                 Report.SymbolRelatedToPreviousError (ae.Location, ae.Name);
 760                                 Report.Error (1537, loc, "The using alias `{0}' appeared previously in this namespace", name);
 761                                 return;
 762                         }
 763
 764                         if (RootContext.Version == LanguageVersion.Default &&
 765                             name == "global" && RootContext.WarningLevel >= 2)
 766                                 Report.Warning (440, 2, loc, "An alias named `global' will not be used when resolving 'global::';" +
 767                                         " the global namespace will be used instead");
 768
 769                         // FIXME: get correct error number.  See if the above check can be merged
 770                         if (extern_aliases != null && extern_aliases.Contains (name)) {
 771                                 AliasEntry ae = (AliasEntry) extern_aliases [name];
 772                                 Report.SymbolRelatedToPreviousError (ae.Location, ae.Name);
 773                                 Report.Error (1537, loc, "The using alias `{0}' appeared previously in this namespace", name);
 774                                 return;
 775                         }
 776
 777                         aliases [name] = new LocalAliasEntry (Doppelganger, name, alias, loc);
 778                 }
 779
 780                 public void UsingExternalAlias (string name, Location loc)
 781                 {
 782                         if (UsingFound || DeclarationFound) {
 783                                 Report.Error (439, loc, "An extern alias declaration must precede all other elements");
 784                                 return;
 785                         }
 786
 787                         // Share the extern_aliases field with the Doppelganger
 788                         if (extern_aliases == null) {
 789                                 extern_aliases = new ListDictionary ();
 790                                 Doppelganger.extern_aliases = extern_aliases;
 791                         }
 792
 793                         if (extern_aliases.Contains (name)) {
 794                                 AliasEntry ae = (AliasEntry) extern_aliases [name];
 795                                 Report.SymbolRelatedToPreviousError (ae.Location, ae.Name);
 796                                 Report.Error (1537, loc, "The using alias `{0}' appeared previously in this namespace", name);
 797                                 return;
 798                         }
 799
 800                         if (name == "global") {
 801                                 Error_GlobalNamespaceRedefined (loc);
 802                                 return;
 803                         }
 804
 805                         // Register the alias in aliases and extern_aliases, since we need both of them
 806                         // to keep things simple (different resolution scenarios)
 807                         ExternAliasEntry alias = new ExternAliasEntry (Doppelganger, name, loc);
 808                         extern_aliases [name] = alias;
 809                 }
 810
 811                 public FullNamedExpression LookupNamespaceOrType (DeclSpace ds, string name, Location loc, bool ignore_cs0104)
 812                 {
 813                         // Precondition: Only simple names (no dots) will be looked up with this function.
 814                         FullNamedExpression resolved = null;
 815                         for (NamespaceEntry curr_ns = this; curr_ns != null; curr_ns = curr_ns.ImplicitParent) {
 816                                 if ((resolved = curr_ns.Lookup (ds, name, loc, ignore_cs0104)) != null)
 817                                         break;
 818                         }
 819                         return resolved;
 820                 }
 821
 822                 static void Error_AmbiguousTypeReference (Location loc, string name, FullNamedExpression t1, FullNamedExpression t2)
 823                 {
 824                         Report.Error (104, loc, "`{0}' is an ambiguous reference between `{1}' and `{2}'",
 825                                 name, t1.FullName, t2.FullName);
 826                 }
 827
 828                 // Looks-up a alias named @name in this and surrounding namespace declarations
 829                 public FullNamedExpression LookupAlias (string name)
 830                 {
 831                         AliasEntry entry = null;
 832                         for (NamespaceEntry n = this; n != null; n = n.ImplicitParent) {
 833                                 if (n.extern_aliases != null && (entry = n.extern_aliases [name] as AliasEntry) != null)
 834                                         break;
 835                                 if (n.aliases != null && (entry = n.aliases [name] as AliasEntry) != null)
 836                                         break;
 837                         }
 838                         return entry == null ? null : entry.Resolve ();
 839                 }
 840
 841                 private FullNamedExpression Lookup (DeclSpace ds, string name, Location loc, bool ignore_cs0104)
 842                 {
 843                         //
 844                         // Check whether it's in the namespace.
 845                         //
 846                         FullNamedExpression fne = ns.Lookup (ds, name, loc);
 847                         if (fne != null)
 848                                 return fne;
 849
 850                         if (extern_aliases != null) {
 851                                 AliasEntry entry = extern_aliases [name] as AliasEntry;
 852                                 if (entry != null)
 853                                         return entry.Resolve ();
 854                         }
 855
 856                         if (IsImplicit)
 857                                 return null;
 858
 859                         //
 860                         // Check aliases.
 861                         //
 862                         if (aliases != null) {
 863                                 AliasEntry entry = aliases [name] as AliasEntry;
 864                                 if (entry != null)
 865                                         return entry.Resolve ();
 866                         }
 867
 868                         //
 869                         // Check using entries.
 870                         //
 871                         FullNamedExpression match = null;
 872                         foreach (Namespace using_ns in GetUsingTable ()) {
 873                                 match = using_ns.Lookup (ds, name, loc);
 874                                 if (match == null || !(match is TypeExpr))
 875                                         continue;
 876                                 if (fne != null) {
 877                                         if (!ignore_cs0104)
 878                                                 Error_AmbiguousTypeReference (loc, name, fne, match);
 879                                         return null;
 880                                 }
 881                                 fne = match;
 882                         }
 883
 884                         return fne;
 885                 }
 886
 887                 // Our cached computation.
 888                 static readonly Namespace [] empty_namespaces = new Namespace [0];
 889                 Namespace [] namespace_using_table;
 890                 Namespace [] GetUsingTable ()
 891                 {
 892                         if (namespace_using_table != null)
 893                                 return namespace_using_table;
 894
 895                         if (using_clauses == null) {
 896                                 namespace_using_table = empty_namespaces;
 897                                 return namespace_using_table;
 898                         }
 899
 900                         ArrayList list = new ArrayList (using_clauses.Count);
 901
 902                         foreach (UsingEntry ue in using_clauses) {
 903                                 Namespace using_ns = ue.Resolve ();
 904                                 if (using_ns == null)
 905                                         continue;
 906
 907                                 list.Add (using_ns);
 908                         }
 909
 910                         namespace_using_table = new Namespace [list.Count];
 911                         list.CopyTo (namespace_using_table, 0);
 912                         return namespace_using_table;
 913                 }
 914
 915                 static readonly string [] empty_using_list = new string [0];
 916
 917                 public int SymbolFileID {
 918                         get {
 919                                 if (symfile_id == 0 && file.SourceFileEntry != null) {
 920                                         int parent_id = parent == null ? 0 : parent.SymbolFileID;
 921
 922                                         string [] using_list = empty_using_list;
 923                                         if (using_clauses != null) {
 924                                                 using_list = new string [using_clauses.Count];
 925                                                 for (int i = 0; i < using_clauses.Count; i++)
 926                                                         using_list [i] = ((UsingEntry) using_clauses [i]).Name.ToString ();
 927                                         }
 928
 929                                         symfile_id = CodeGen.SymbolWriter.DefineNamespace (ns.Name, file.SourceFileEntry, using_list, parent_id);
 930                                 }
 931                                 return symfile_id;
 932                         }
 933                 }
 934
 935                 static void MsgtryRef (string s)
 936                 {
 937                         Console.WriteLine ("    Try using -r:" + s);
 938                 }
 939
 940                 static void MsgtryPkg (string s)
 941                 {
 942                         Console.WriteLine ("    Try using -pkg:" + s);
 943                 }
 944
 945                 public static void Error_GlobalNamespaceRedefined (Location loc)
 946                 {
 947                         Report.Error (1681, loc, "You cannot redefine the global extern alias");
 948                 }
 949
 950                 public static void Error_NamespaceNotFound (Location loc, string name)
 951                 {
 952                         Report.Error (246, loc, "The type or namespace name `{0}' could not be found. Are you missing a using directive or an assembly reference?",
 953                                 name);
 954
 955                         switch (name) {
 956                         case "Gtk": case "GtkSharp":
 957                                 MsgtryPkg ("gtk-sharp");
 958                                 break;
 959
 960                         case "Gdk": case "GdkSharp":
 961                                 MsgtryPkg ("gdk-sharp");
 962                                 break;
 963
 964                         case "Glade": case "GladeSharp":
 965                                 MsgtryPkg ("glade-sharp");
 966                                 break;
 967
 968                         case "System.Drawing":
 969                         case "System.Web.Services":
 970                         case "System.Web":
 971                         case "System.Data":
 972                         case "System.Windows.Forms":
 973                                 MsgtryRef (name);
 974                                 break;
 975                         }
 976                 }
 977
 978                 /// <summary>
 979                 ///   Used to validate that all the using clauses are correct
 980                 ///   after we are finished parsing all the files.
 981                 /// </summary>
 982                 void VerifyUsing ()
 983                 {
 984                         if (extern_aliases != null) {
 985                                 foreach (DictionaryEntry de in extern_aliases)
 986                                         ((AliasEntry) de.Value).Resolve ();
 987                         }
 988
 989                         if (using_clauses != null) {
 990                                 foreach (UsingEntry ue in using_clauses)
 991                                         ue.Resolve ();
 992                         }
 993
 994                         if (aliases != null) {
 995                                 foreach (DictionaryEntry de in aliases)
 996                                         ((AliasEntry) de.Value).Resolve ();
 997                         }
 998                 }
 999
1000                 /// <summary>
1001                 ///   Used to validate that all the using clauses are correct
1002                 ///   after we are finished parsing all the files.
1003                 /// </summary>
1004                 static public void VerifyAllUsing ()
1005                 {
1006                         foreach (NamespaceEntry entry in entries)
1007                                 entry.VerifyUsing ();
1008                 }
1009
1010                 public string GetSignatureForError ()
1011                 {
1012                         return ns.GetSignatureForError ();
1013                 }
1014
1015                 public override string ToString ()
1016                 {
1017                         return ns.ToString ();
1018                 }
1019         }
1020 }